It has been known that a considerable force is required to attain a full closure of a vehicle door not only because of the force required to fully latch the striker mounted on the vehicle body to the latch mechanism mounted on the vehicle door but also because of a strong resistance which the weather strip exerts against the force to close the door. To overcome this problem, U.S. Pat. No. 4,707,007 issued to Inoh and assigned to one of the joint assignees of the present application proposed an active door latch assembly which is provided with a striker mounted on a vehicle body so as to be moveable toward and away from the center of the vehicle body by a certain stroke; a latch mechanism mounted on a closure member such as a door for latching the striker thereto upon closing of the closure member upon the vehicle body; powered drive means for moving the striker toward and away from the vehicle body; a door switch for detecting an almost fully closed state of the door; and timer means for activating the powered drive means so as to move the striker towards the vehicle body shortly after the door switch has detected the almost fully closed state of the door, and away from the vehicle body when the door switch is slightly opened by unlatching the door.
According to this proposal, the door switch is required to be finely adjusted so as to detect the latched and unlatched state of the latch mechanism with a reasonable accuracy. However, it means a small dimensional tolerance, and requires considerable care in applying this invention to industrial applications. Additionally, the use of the timer involves a delayed action of the powered drive means, which may be helpful in increasing the safety of the system but may not be very attractive to the user of the vehicle.